Electrical heating element



June 26, 1923.

A I 1,460,,8 'OFFIC PERCY A. E. ARMSTRONG, OF LOUDONVILLE, AND RALBH 1".DE VRIES, OF NEWTON- VILLE, NEW YORK; SAID DE VRIES ASSIGNOB TO SAIDARMSTRONG.

ELECTRICAL HEATING ELEMENT.

We Drawing.

To all whom it may concern Be it known that we, PERCY A. E. ARM- STRONG,a subject of the King of Great Britain, and a resident of Loudonville,county of Albany and State of New York, and RALPH P. DE VRIEs, a citizenof the United States, and a resident of Newtonville, county of A1 bany,and State of New York, have invented certain new and useful Improvementsin Electrical Heating Elements, of which the following is aspecification.

- Our invention relates to elements for electrical heating purposes,which may be either mechanically worked as by hot or cold rolling, wiredrawing or the like, or may be in the form of cast grids or the like.Electrical heating elements in accordance with our invention are made ofalloy steel containing iron, chromium, silicon, a high melting pointmetal or metals other than chromium of the sixth, group of Mendelefistable preferably tungsten, .and carbon; and may contain chromium fromabout to about silicon from about .5% to about 3.5% or 4% formechanically worked material, and up to about 6% silicon for eastmaterial, tungsten from about 2% to about 5% for readily mechanicallyworked material and up to about 10% where the consequent red hardnessis" not objectionable, carbon from about .05 to about 1%, and theprincipal part of the remainder is made up of the iron base. Thematerial may contain more or less sulfur or other metalloids, but theproportion of metalloids other than silicon is preferably kept low.Manganese may also be present in the usual proportions encountered insteel making, say up to about 1%. Higher percentages are not-desirable,and the manganese may be dispensed with, if desired. Molybdenum oruranium may be substituted for the tungsten or part thereof if desired,with nearly if not'quite so good results as with the tungsten.

We have obtained very good results, for example, from electrical heatingelements run at about 1700 to 1900 F., and made from alloy steelcontaining carbon about .20

to 30%, chromium about 17 to 20%, silicon about 2.40 to 3%, tungstenabout 2.5 to 3%,

manganese about .20 to .40%, and the principal part of the remainderiron, one of several melts being ofv the following analysis: carbonabout 25%, chromium about Application filed m 29,

1921. Serial No. 488,471.

18%, silicon about 3%, manganese about 7 40%, tungsten about 3%, and theprincipal part of the remainder iron.' This material when put into useas an electrical heatingv element, run up to about the temperaturesreferred to, shows a smooth whitish surface formation which may bereferred to as a frosting or an excessively thin scale, and is subjectto practically no progressive deterioration or scale formation in use,so that the body of the metal is not called upon to give up additionalmetal to form an oxide,'and the material stands up extremely well in useover long periods. To obtain this result with a whitish frosting orscale, we have found that at least 2% of silicon should be present andpreferably about 2.4%. This whitish frosting appears to some extent with3% of silicon as used in the foregoing example when as little as 2% oftungsten is used, and with 3% of tungsten as in the foregoing examplethe whitish frosting effect is obtained to substantially a maximumextent; It appears essential to produce the whitish scale or frosting,which is apparently non-porous and serves as a protection againstdeterioration of the metal when run at high temperatures, that aconsiderable body of silicon should be present together with thetungsten. For electrical resistance material as an electrical heatingelement, but while carbon above aboutv.4% is not recommended for heatingelements, same may be higher up to about 1%, particularly for electricalresistance elements which are used at comparatively low temperatures.The proportions given herein are by weight.

The alloy of the present invention is resistant to rusting and to theaction of acids and other corroding agents and may be made use of wherethese characteristics are of advantage as, for example, it is welladapted for such uses as heating of liquids by means of .bare electricalheating ele ments submerged inand brou ht into direct contact with theliquid to e heated.

The specific resistance of elements in accordance withrthis invention iscomparatively hi h use of elements of relatively small crosssection. Forexample, elements containing,

carbon .1 to 4%, s1l1con 2.4 to 3.5%, tungstenu25 to 5%, manganese under1%, and' the principal part of the remainder-except for chromium-iron,we'find that with chromium 17 to 20%, ,the material. has .a specificresistance of about 100 microhms per cubic -c. cs; with the samematerial except that the chromium" is from 20 'to25%,' the specificresistance is about 105 microhms per cubic 'c. 0.; and with 25 to ofchromi um, the specific resistance" is'about 110'.

microhms per cubic c. c.

We claim: 1. An electrical heating element made of alloy steelcontaining 'carbon about .05v to 1%, chromium more than, 10% and lessthan 30%, silicon about 2 to 6%, a high melting point metal or metalsother-than chromium of the sixth. group of Mendelefis table about .20 toabout: 10%, and the principal part of the remainder iron.

2. An electrical heating element inade of alloy steel containing carbonabout .05 to 1%, chromium more than 10% and less than 30%, siliconabout2 to 6%,"tungsten. about .20 to 10%, and the principal part of theremainder iron. l L

'3. Amchanically worked electrical heating element made of alloj steelcontaining carbon about .05 to .4%, chromium about 17 to 25%, siliconabout 2 to "3.5%, tungsten about .20to 5%,and the principal part of theremainder 'irbn. i

4. An electrical "heating element made' of so that -it is possible tomake alloy steel containing carbon about .1 to

.-4%, chromium about 17 .to 25%, silicon alloysteel containing carbonabout -.1 to" .4%, chromium about 18%,, siliconabout.

3%, tungsten about 3%, manganese under 1%, and the principal part of theremainder,;iron-.-

.7 electrical heating element made of alloy steel. containin :carbon,chromium, silicon, tungsten an 0 iron, with; v at least as much SillOOD.as tungsten and exhibiting a whitish frosting or scale of excessivethin;

ness when; subjected to electrical heating at about'l'ZOO to 1900 F.

8.;An electrical resistance element made of alloy steel containingcarbon about .05 to 1%, chromium about 10.to 30%, tungsten about ,20'to.1 0%, siliconlabout .5 to 6%,

and-"the principal part of the remainder 11011- 9, An electricalresistance element madeof alloy steel containing carbon about .05

to 1%,chromium "about 17 25%, silicon about .5 tojl3.'5%, tungsten about2 t0 5%. manganese" under' 1%, and the principal part of the remainderviron.

, In testimonythat'we claim the foregoing,

we have s'ignedourn'ames hereto.

PERCY A. ARMSTRONG, RALPHRDE VRIEs. a

